The groups said the environmental danger of oil tankers traveling through the coastal waters of British Columbia is too great, and the announcement could set the stage for a protracted legal and political fight over the pipeline.

"Some people are saying (the pipeline) is a done deal. It's not," Art Sterritt, executive director of the Coastal First Nations, a coalition of native Indian communities in the rugged wilderness area, often called the Great Bear Rainforest.

Canada's courts have ruled native groups must be consulted about projects built on their historic territories.

The proposed project would carry crude from the oil sands in northern Alberta to a port facility in Kitimat, British Columbia.

Aboriginal leaders said their opposition to the project was strong enough for them to continue the fight, even if Enbridge gets government and court permission to build it -- including blockading tankers.

"We are prepared to put boats across the channel," Gerald Amos, a director of the coalition and a native leader from the Kitimat area, told reporters at a news conference in Vancouver.

The groups announced their opposition on the 21st anniversary of the Exxon Valdez tanker's massive oil spill in Alaska. And the Vancouver announcement was accompanied by national newspaper ads comparing the two events.

Steve Wuori, vice-president of liquids pipelines for Enbridge Inc, Canada's second-largest pipeline company, told the Reuters Canadian Oil Sands Summit in Calgary that he was frustrated by the comparison to the Valdez disaster.

"It's disappointing to see the dialogue over what is an important infrastructure project under stringent environmental standards and engineering practices reduced to a recounting of a 21-year-old incident," Wuori said.

Tankers used today are safer and the company has pledged to install an emergency response system, Wuori said.

The Exxon Valdez accident lead to restrictions on oil tanker traffic on Canada's Pacific coast. The aboriginal groups said Enbridge's line will bring as many as 150 ships to Kitimat each year.

Enbridge expects to file for regulatory approvals for the 525,000 bpd line by mid-year and expects a decision from federal regulators to take 18 months or more. The line would not be in service before 2015. the company said.

The aboriginal groups hope their unified opposition would encourage the British Columbia provincial government to also come out against the pipeline.

British Columbia energy minister Blair Lekstrom said on Tuesday he would not take a position until Enbridge presents its full plan to regulators, but he also noted the project could bring needed jobs to the region.